安卓MVVM最簡demo(ViewModel+LiveData+Room+Paging)

摘要： 簡要介紹 本demo按照MVVM方式實現最簡單的資料展示(支援自動分頁載入)和刪除的demo,用於展示一個完整的MVVM架構. 包含:ViewModel+LiveData+Room+Paging 語言:Kotlin 採用kotlin coroutines實現資料庫...

簡要介紹

本demo按照MVVM方式實現最簡單的資料展示(支援自動分頁載入)和刪除的demo,用於展示一個完整的MVVM架構.

1. 包含:ViewModel+LiveData+Room+Paging
2. 語言:Kotlin
3. 採用kotlin coroutines實現資料庫操作
4. 不包含databinding(對方比較之後,覺得databinding不夠靈活而且還存在一些問題,具體百度搜索.不過demo裡其實也附帶了一個包含databinding的例子)

程式碼實現(只貼出重點程式碼,完整程式碼見原始碼)

1. UserActivity

class UserActivity : AppCompatActivity() {
private lateinit var viewModel: UserViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_user)
val factory = InjectorUtils.provideUserViewModelFactory(this)
viewModel = ViewModelProviders.of(this, factory).get(UserViewModel::class.java)
val adapter = UserAdapter()
adapter.setOnItemClick { user ->
viewModel.delUser(user.id)
}
userRv.adapter = adapter
viewModel.userList.observe(this, Observer { adapter.submitList(it) })
}
}

2. UserAdapter

class UserAdapter : PagedListAdapter<User, UserAdapter.ViewHolder>(UserDiffCallback()) {
private lateinit var onItemClick: (user: User) -> Unit
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val data = getItem(position) ?: return
holder.itemView.userTv.text = data.name
holder.itemView.setOnClickListener { onItemClick(data) }
}

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.item_user, parent, false)
return ViewHolder(view)
}

infix fun setOnItemClick(onClick: (user: User) -> Unit) {
this.onItemClick = onClick
}

class ViewHolder(itemView: View?) : RecyclerView.ViewHolder(itemView!!)
}

private class UserDiffCallback : DiffUtil.ItemCallback<User>() {
override fun areContentsTheSame(oldItem: User, newItem: User): Boolean {
return oldItem.id == newItem.id
}

override fun areItemsTheSame(oldItem: User, newItem: User): Boolean {
return oldItem == newItem
}
}

3. UserViewModel

class UserViewModel internal constructor(private val userRepository: UserRepository) : ViewModel() {
val userList = userRepository.getUserList()

fun delUser(id: Int) {
GlobalScope.launch {
userRepository.delUser(id)
}
}
}

4. UserRepository

class UserRepository private constructor(private val userDao: UserDao) {

fun getUserList() = userDao.getUserList().toLiveData(Config(
pageSize = 30,
enablePlaceholders = true))

suspend fun addUser(name: String) {
withContext(Dispatchers.IO) {
val user = User(0, name)
userDao.add(user)
}
}

suspend fun delUser(id: Int) {
withContext(Dispatchers.IO) {
val user = User(id, "")
userDao.del(user)
}
}

companion object {
@Volatile
private var instance: UserRepository? = null

fun getInstance(userDao: UserDao) =
instance ?: synchronized(this) {
instance
?: UserRepository(userDao).also { instance = it }
}
}
}

5. UserDao

@Dao
interface UserDao {
@Query("SELECT * FROM User")
fun getUserList(): DataSource.Factory<Int, User>

@Insert
fun add(user: User)

@Insert
fun add(users: List<User>)

@Delete
fun del(user:User)
}

Demo原始碼

https://gitee.com/cxyzy1/mvvmDemo.git

安卓開發技術分享: https://www.jianshu.com/p/442339952f26

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